实现读取PDM信号的文件并将其转换为PCM信号的完整代码：

以下是使用 STM32F103RC 单片机实现读取 PDM 信号并转换为 PCM 信号的示例代码：

#include "stm32f1xx_hal.h"
#include "PDMFilter_Keil.h"

#define PDM_BUFFER_SIZE 64
#define PCM_BUFFER_SIZE 512

UART_HandleTypeDef huart1;
I2S_HandleTypeDef hi2s2;

uint16_t pdm_buffer[PDM_BUFFER_SIZE]; // PDM 缓冲区
int16_t pcm_buffer[PCM_BUFFER_SIZE]; // PCM 缓冲区

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART1_UART_Init(void);
static void MX_I2S2_Init(void);

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART1_UART_Init();
  MX_I2S2_Init();

  while (1)
  {
    // 读取 PDM 数据
    HAL_I2S_Receive(&hi2s2, (uint16_t *)pdm_buffer, PDM_BUFFER_SIZE, 1000);

    // 进行 PDM 到 PCM 转换
    PDM_Filter(pdm_buffer, pcm_buffer, PDM_BUFFER_SIZE, &PDM_FilterHandler);

    // 发送 PCM 数据
    HAL_UART_Transmit(&huart1, (uint8_t *)pcm_buffer, PCM_BUFFER_SIZE * 2, 1000);
  }
}

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
                              | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_I2S2_Init(void)
{
  hi2s2.Instance = SPI2;
  hi2s2.Init.Mode = I2S_MODE_MASTER_RX;
  hi2s2.Init.Standard = I2S_STANDARD_MSB;
  hi2s2.Init.DataFormat = I2S_DATAFORMAT_16B;
  hi2s2.Init.MCLKOutput = I2S_MCLKOUTPUT_DISABLE;
  hi2s2.Init.AudioFreq = I2S_AUDIOFREQ_48K;
  hi2s2.Init.CPOL = I2S_CPOL_LOW;
  hi2s2.Init.ClockSource = I2S_CLOCK_PLL;
  hi2s2.Init.FullDuplexMode = I2S_FULLDUPLEXMODE_DISABLE;
  if (HAL_I2S_Init(&hi2s2) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_USART1_UART_Init(void)
{
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOC_CLK_ENABLE();

  // 配置 I2S 接口引脚
  GPIO_InitStruct.Pin = GPIO_PIN_3 | GPIO_PIN_4 | GPIO_PIN_5;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF5_SPI2;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  // 配置 UART1 引脚
  GPIO_InitStruct.Pin = GPIO_PIN_9;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}

void Error_Handler(void)
{
  // 错误处理函数
  while (1)
  {
  }
}

需要注意的是，上述代码中使用了 libPDMFilter_Keil 库进行 PDM 到 PCM 的转换。如果您没有该库，可以在 Keil 官网下载并添加到您的工程中。另外，具体的配置参数需要根据您的实际硬件环境进行调整。